OCW Logic

[Rick Ratzlaff]

I have done ladder tests for years and it makes some sense to me. However, it has always been on medium size caliber to 7MMRM. I have a friend with a 223 Rem and we intend to hand load for him. I have never done such a small case before. I intend to teach him how to hand load.

This has created some new questions. I have watched and read many stories from top shooters who use the "OCW" process. And I have read the instructions for the OCW method. So we decided that because we are starting from scratch we will follow the OCW instructions. Therefore I dug deeper into the methodology.

I find something interesting that does not make sense to me.

The table created looks like this.

Minimum	23.5
Maximum	24.9
Rnd 10	24.9	-E21 the MAXIMUM Load
Rnd 9	24.8	=G28*(1-0.5%)
Rnd 8	24.7	=F28*(1-0.5%)
Rnd 7	24.5	=F28*(1-0.5%)
Rnd 6	24.4	=D28*(1-0.7%)
Rnd 5	24.2	=C28*(1-0.7%)
Rnd 4	23.9	=G26*(1-1%)

The formulas work just fine. But my question is:

1. What is the logic to take the % reduction from 0.5% to 1% ?
2. What is the logic in this format to be the same for a 223, a 7mmRM and a 338? My simple math says that any percentage change will have a significant difference between cases of different volumes. Therefore the percentage shift should be based on relative case size. +/-

When I use my old (really old) method. I would ladder test for a 223-in- .1 grain increment, my 243 in .2 or .3-grain increments, and my 7mm Rem mag in .5-grain increments for the first run or test.

I hope I'm clear. Can someone enlighten me? Thanks

Corrected. I missed my decimal on the grain increments.

 

[762plinker]

so IMHO ocw is a waste of time and components
simple single shot ladder in small steps up max plus( all guns differ, just stop shooting when the gun tells you)
log velocity and shot number/location
this is a starting point do actual load development from this data
1/100 of case volume is a good increment...your steps are too big

 

[Ackley Kid]

When running OCW ( optimal charge weight ) you are looking for point of impact only . Your looking for a trend in POI so in saying this if you run charge weights in 1.0 gr increments you can skip right over what your looking for . On the other extreme running 0.1 charge weights makes for a lot of overlap ( and ammo )in what your trying to see . It’s best accomplished at 100 yards ( 3 shot groups )Eric Cortina had a thread describing his process , with tons of info that may be of interest to you . Many people are chasing different things with this ie small group , ES,SD . What it does is show your barrels preferred charge weight or where the barrel is stable and repeatable .

As noted above by 762plinker ladders use less components and are suited to longer distances ( usually distance your discipline requires ) 600 yard BR guys would tune up at 600 ECT , ECT . Most usually start with a rough ladder (0.3-0.5 ) and fine tune in 0.1 increments. Most don’t start serious load development till you have some rounds on a new barrel which gives you some rounds to play with seating depth a bit and run OCW if you chose .
Both work so pick your poison! I use both and run OCW and mess with seating depth for the first 100 rounds or so and shift to short ladders and group tuning after I’ve seen barrel speed up .

 

[Ackley Kid]

I believe this was a target from Erics thread that had 2000+ posts .

 

[Jarhead6870]

Rick…you have a PM

 

[Rick Ratzlaff]

Thanks, guys. I screwed up by missing my decimal points on power charge increments. It is corrected. Kinda elementary

 

[Rick Ratzlaff]

so IMHO ocw is a waste of time and components
simple single shot ladder in small steps up max plus( all guns differ, just stop shooting when the gun tells you)
log velocity and shot number/location
this is a starting point do actual load development from this data
1/100 of case volume is a good increment...your steps are too big

Ya no kidding. I knew better. Spelling screwup in my old age.

 

[jelenko]

The steps may depend on the level of accuracy you're looking for.
In XTC, we're looking for ~ 1/2 MOA groups and use .2gr steps for 223.

 

[762plinker]

When running OCW ( optimal charge weight ) you are looking for point of impact only . Your looking for a trend in POI so in saying this if you run charge weights in 1.0 gr increments you can skip right over what your looking for . On the other extreme running 0.1 charge weights makes for a lot of overlap ( and ammo )in what your trying to see . It’s best accomplished at 100 yards ( 3 shot groups )Eric Cortina had a thread describing his process , with tons of info that may be of interest to you . Many people are chasing different things with this ie small group , ES,SD . What it does is show your barrels preferred charge weight or where the barrel is stable and repeatable .

As noted above by 762plinker ladders use less components and are suited to longer distances ( usually distance your discipline requires ) 600 yard BR guys would tune up at 600 ECT , ECT . Most usually start with a rough ladder (0.3-0.5 ) and fine tune in 0.1 increments. Most don’t start serious load development till you have some rounds on a new barrel which gives you some rounds to play with seating depth a bit and run OCW if you chose .
Both work so pick your poison! I use both and run OCW and mess with seating depth for the first 100 rounds or so and shift to short ladders and group tuning after I’ve seen barrel speed up .

no,a real simple ladder works well at all distances. the long range only comes form a posted"untruth" else where in the internet.
ladder has been around and used alot before a guy could not figure out the simple process and started wasting components with ocw

 

[CharlieNC]

OCW is a form of a ladder test, with the major strength of shooting the shots in a round robbin sequence to average out the time related changes such that the poi center is very robust. But I personally like 200yd....

 

[Ackley Kid]

Sorry if I miss read your post Rick was not trying to be smart

 

[mikecr]

I see OCW as helping find a powder node. A forgiving load.
Ladder for finding a barrel node. Cutting edge precision.
Given this, both can be done -with a barrel tuner.
Otherwise, you may or may not get lucky enough for best of both.

I see primer swapping, seating testing, and brass fire forming as prerequisites to load development.
They're not tuning

 

[Ned Ludd]

OCW can work very well for load development, especially if shorter distances of 100-200 yd or so are all that are available. Trying to interpret a ladder test fired at such short distances in a meaningful way can be challenging at best. Here is a link to Erik Cortina's thread regarding the use of OCW for load development:

Long range load development at 100 yards.

I found this target, and I think it's a perfect example of how some people might choose the wrong load because they fell in love with a group without reading the groups properly. This target was shot with my 6.5x47 Lapua and 139 gr. Lapua Scenars with VV N550 powder. At plain sight, 38.5 gr...

forum.accurateshooter.com

The major reasons for defining the upper and lower charge weight limits for testing purposes include A) SAFETY and B) so as to cover a charge weight range that is actually useful for the specific cartridge/rifle setup and thus likely to provide a solid candidate charge weight for further development, but without unnecessarily wasting components. Selecting the proper range for a given cartridge/powder/bullet weight combination can be done in a variety of ways, including using percentages such as the OP was asking about, data from a reloading manual, or the use of a reloading program such as QuickLoad or GRT. Regardless, the idea is pretty simple...you don't want to reach a charge weight that is dangerous at the high end, or one that is so low that it results in testing a bunch of charge weights that are unlikely to provide even reasonably acceptable velocity at the low end.

Deciding on the appropriate charge weight interval to use is also not written in stone. I tend toward using a smaller increment initially than some might choose, let's say something like no more than a 0.1 to 0.2 gr increment for a small case such as .223 Rem, and a 0.2 to 0.3 gr increment for larger cases such as .308 Win or .30-06. The choice might depend on whether I wanted to start with a streamlined, or "coarse" charge weight test, just to identify a likely charge weight region to test further using a finer increment. Alternatively, if I already had some idea of where a load was likely to end up, I might go straight to 0.1 gr increments. If one starts with a fairly coarse interval initially, it is likely they will end doing additional testing later using a finer increment, so it's not like either approach ends up being significantly less effort/components. There is no single "correct" way to do this as different paths can end up at the same place.

 

[1shot]

I believe this was a target from Erics thread that had 2000+ posts .

Now that I "see" what OCW is, it all makes sense. thanks for this post.

Lloyd

 

[Doom]

I'll add one item to the above. In 223 what we see as nodes is not always obvious in that the points of impact tend deviate slightly on either side unlike larger capacity cartridges where the nodes are wider. What I do is use 0.2 grain increments and when I think I have a node I repeat with 0.1gr on either side to verify it's good. It also helps to overlay your groups to see how they group together.